Lung infections by Mycobacterium avium and Mycobacterium abscessus are increasing in incidence. Diseases caused by both Mycobacteria are common in patients with chronic lung conditions, such as cystic fibrosis (CF), non-CF bronchiectasis and emphysema. In patients with AIDS, the M. avium infection is disseminated. The current clinical paradigm is to treat patients with M. avium or M. abscessus lung infections or M. avium disseminated infection with combination therapy given orally or by IV. Unfortunately, these therapies often fail. Thus, there is a need to develop new anti-mycobacterial therapies for both diseases. The overall objective of this project is test the efficacy of two new formulations of ciprofloxacin (Ciprofloxacin for Inhalation, CFI, Lipoquin(R); and Dual Release Ciprofloxacin for Inhalation, DRCFI, Pulmaquin(R)), developed recently specifically for inhalation a) alone and b) in combination with other anti- mycobacterial agents using in vitro and in vivo models of M. avium and M. abscessus lung infection and M. avium disseminated infection. The superior formulation(s) will then be taken into human clinical trials. Both formulations are comprised of ciprofloxacin encapsulated in liposomes, which provide sustained slow release of the ciprofloxacin from the liposome, allowing for once-daily dosing. The DRCFI formulation is a mixture of CFI and free ciprofloxacin, a non-liposomal solution. The rationale for developing DRCFI is to combine the advantages of an initial transient high concentration of free ciprofloxacin to increase maximum levels in the lung from the free ciprofloxacin component of DRCFI, followed by the slow release of ciprofloxacin from the CFI (liposomal component). Another advantage of these formulations is that the liposomes are avidly ingested by macrophages, bringing the ciprofloxacin into close proximity to the intracellular pathogens, thus further increasing anti-mycobacterial efficacy of the liposomal formulation compared to free ciprofloxacin alone. The specific aims are: 1) to test different concentrations of CFI and DRCFI in the macrophage test system: a) alone and in combination with clarithromycin, ethambutol, and amikacin against 3 clinical isolates of M. avium; b) alone and in combination with imipenem, cefoxitin, and amikacin against 3 clinical isolates of M. abscessus; 2) to test the same regimen of antibiotics against biofilms of M. abscess us and M. avium; 3) to test the in vivo efficacy of CFI and DRCFI in a mouse model of M. avium or M. abscess us lung infection; and 4) to test the same regimen as Aim 3 for M. avium in a mouse model of M. avium disseminated infection. If an efficacious treatment with CFI or DRCFI (alone or in combination with other drugs) is identified, we will progress into clinical studies in patiens with M. avium or M. abscessus lung infection or with M. avium disseminated infection, including those patients with HIV/AIDS. Aradigm already has sufficient safety data in humans and animals to support long-term clinical studies in patients with CFI and DRCFI as well as sufficient cGMP manufacturing in place to support large-scale clinical trials.